This invention relates to a plating process and its means wherein an accurate plating can be carried out on a partitive work surface.
Today, there are being practiced various kinds of partitive plating processes and their means. However, these conventional techniques have the following defects and disadvantages.
(1) A sufficient supply of metal ion is impossible and an electric current density is, for example, of a low level of 20 to 30 A/dm.sup.2. Accordingly, a plating process requires a longer time and its plating apparatus is large-scale.
(2) Although there is used a specific mask for covering a work surface, a circumference of a plated part is apt to become blurred. In other words, a profile of the plated part has no accurate definition. Therefore, the smaller the work surface becomes, the worse the plating finish becomes.
(3) In case the work surface is of a specifically modified shape, it takes a plenty of time to substitute a mask or the like. This is a defective bottleneck of high productivity.
The essential significance of a partitive plating is to plate exclusively a truly necessary part on the work surface. This can contribute to curtail greatly production cost of industrial products. Further, it has a very effective meaning when treating a smaller work surface with a decorative plating. For example, in case of an electric contactor, a partitive gold plating for a work surface of only less than 1 mm .phi. is quite sufficient. Further, when bonding a chip of a semiconductor such as IC to a terminal, a partitive gold plating for a very small work surface of less than 0.4 mm .phi. is quite satisfactory.
Thus, an effective plating is to treat a necessary work surface with an accurate plating.